A controllable design of ZIF-67 based magnetic carbon nanotubes as efficient oxidase mimetics for sensitive detection of alkaline phosphatase in serum

The activity of alkaline phosphatase (ALP) is related to various pathological processes. Therefore, developing an ALP activity detection technology with high sensitivity and accuracy is of great significance for clinical diagnosis and cancer screening. To solve uncontrollable carbon nanotubes (CNTs) structure and lack of solubility, FeCo hollow nanocages (HNCs)@CNTs catalysts were prepared by facile pyrolysis of ZIF-67 precursor mixed with Fe-Co catalyst, displaying an oxidase-like activity. From the characterization, formation of CNTs was observed on the surface of FeCo HNCs@CNTs with the mole ratio of Fe3+ to Co2+ of 3:1. Density functional theory calculations demonstrated that the performed catalytic activity of FeCo HNCs@CNTs derived from active orbital of Co-3d band, which enabled the activation and decomposition of O2 with a feasible thermodynamic process. ·O2− and 1O2 were the main reactive oxygen species as electron acceptors. ALP catalyzed the hydrolysis of ascorbic acid 2-phosphate (AAP) to convert it into ascorbic acid (AA), which could effectively reduce the FeCo HNCs@CNTs-mediated chromogenic reaction of TMB oxidation. The performance of the FeCo HNCs@CNTs-linked biosensing assay showed a broad detection range from 0.1 U/L to 150 U/L and a relatively low limit of detection of 0.083 U/L. The ALP activity of the mouse serum sample obtained by the proposed biosensing assay was highly consistent with that via the clinical method, indicating a promising technology in biomolecule detection.